Various objects such as improvement of productivity or improvement of the quality of products can be achieved by pest control in agricultural production sites such as fields. Thus, various studies regarding pest control have been conducted. It has been desired that a disinfestant comprising an insect growth inhibitor as a main component will be developed, for example.
Molting and/or metamorphosis are characteristic phenomena of insects. Such molting and/or metamorphosis of insects are controlled by hormones. It has been known that molting and/or metamorphosis of insects are controlled by a steroid hormone, ecdysteroid. First, ecdysteroid synthesized in the body of an insect binds to a heterodimer consisting of a molting hormone receptor and USP (ultraspiracle) existing in the nucleus through the cell membrane, so as to form a complex. Subsequently, this complex binds to a response sequence existing upstream of an early gene cluster, so as to induce the expression of the early gene cluster. Thereafter, as a result of the expression of the early gene cluster, the expression of a gene cluster associated with the molting and/or metamorphosis of the insect is promoted, and the molting and/or metamorphosis of the insect progresses.
Thus, it has been known that a molting hormone receptor is located at the uppermost stream of a signaling pathway during the molting and/or metamorphosis of an insect. Accordingly, it is said that a search for a substance inhibiting the binding of ecdysteroid to a molting hormone receptor that is used as the aforementioned insect growth inhibitor is effective for the development of a disinfestant.
However, a method for screening such a substance that inhibits the binding of ecdysteroid to a molting hormone receptor has not yet been established. A substance that is effective as a disinfestant could not easily be screened. As a system for screening an insect growth inhibitor, screening systems such as a system using an insect as a whole, a system using a portion of tissues such as epidermis, or a system using cultured cells have conventionally been known (refer to Non-Patent Documents 1 to 4). However, under the present circumstances, almost no studies have been conducted regarding the screening of an insect growth inhibitor at a molecular level (protein level).
Non-Patent Document 1
Kenichi Mikitani Appl. Entomol. Zool. 31 (4): 531-536
A novel ecdysone responsive reportaer plasmid regulated by the 5′-upstreme region of the Drosophila melanogaster (Diptera; Drosophilidae) acethylcholinesterase gene
Non-Patent Document 2
Kenichi Mikitani J. Insect Physiol. 42: (10) 937-941 October 1996
Ecdysteroid receptor binding activity and ecdysteroid agonist activity at the level of gene expression are correlated with the activity of dibenzoyl hydrazines in larvae of Bombyx mori 
Non-Patent Document 3
Kenichi Mikitani BIOCHEM. BIOPHYS. RES. COMMUN. 227: (2) 427-432 Oct. 14, 1996
A new nonsteroidal chemical class of ligand for the ecdysteroid receptor 3,5-di-tert-butyl-4-hydroxy-N-isobutyl-benzamide shows apparent insect molting hormone activities at molecular and cellular levels
Non-Patent Document 4
Trisyono A, Goodman C L, Grasela J J, et al. IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-ANIMAL 36: (6) 400-404 June 2000
Establishment and characterization of an Ostriniia nubilalis cell line, and its response to ecdysone agonists
Thus, taking into consideration the aforementioned actual situation, it is an object of the present invention to provide a completely novel molting hormone receptor and a method for screening a ligand binding thereto, so as to efficiently screen a substance that can be applied to a disinfestant or the like.